Things I have learned....
Necro Summoning is simply useful Homonculi
Necro Magicians should prob be aspected sorcerers, focusing on ritual spellcasting, that can do something else besides necro summoning. Regular summoning is just too convenient and easy for full magicians for Necro Magicians to take on a magical specialist role. That having a necro spirit reduces effective Magic rating and Magicians will need at least Magic 8 to get at least two at a time, investing in regular magic is simply just more efficient.
Dedicated Spellslinger might be worth it, but the investment in spellcasting skill might not be worth the karma costs for more starting spells.
Death and Dark King are dumb mentor spirits. Contractual Rituals are so niche and GM specific, and Death seemingly gives bonuses to folks who would be good at medical skills (combined with a Logic drain stat), but hinders characters with mentor disadvantage to overcome to heal anyone. Not taking a mentor spirit makes going aspected even less worthwhile.
What Necros can be good at:
Rituals! Rituals as neat secondary can be fun and Necros make them worthwhile. Magic specialists usually dont take it, so a necro with a different role can use rituals without stepping on toes. Rituals are great for aspected magicians because they aren't limited by Magic rating (so low magic investment is ok), ritual foci are relatively cheap in cost/karma, and spell ritual foci can be used for any non-spell ritual (including the minions of necro). So even with low magic, it is easy to cobble enough ritual dice necro summon.
Spirits that last long time, that are cheaper than bound spirits, and you have unlimited services from. These are great for mostly non-combat purposes. It is like having a mini allied spirit that has more than very limited uses like homonculi.
Role ideas this pairs with:
Decker Necros: Just uses the Logic Drain synergy to make a low Magic decker with a twist. Spirits are always nice meat guards when in VR or to help get jacks and taps into hard to reach places. Can also be combined with VR van deckers who use rituals to boost attributes.
Alterna-Logic Necros: Sometimes there is room on a team for someone who can can excel in non-matrix logic skillsets. Someone who can do the Engineering, First Aiding, Demolitions, Chemistry, Forging, etc. A knowledge seeker/pro pairs well with someone studying the Black domain of Magic.
Anti-Private Eyes/Bounty Hunters - Basically social focused characters that aren't afraid to get mean. Nothing screams intimidation bonuses like sending corpses of dead pets (carcass) or even of "recently deceased" loved ones (corpse) to harass someone, let alone fight them. Or bringing back grandparents from cremated remains of stolen urns (palefire or detrius) Additionally, having spirits that can help over the course of several days of legwork without being interrupted by sunrise/sets can be useful.